/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.druid.catalog.sync;

import org.apache.druid.guice.ManageLifecycle;
import org.apache.druid.java.util.common.lifecycle.LifecycleStart;
import org.apache.druid.java.util.emitter.EmittingLogger;

import javax.inject.Inject;

/**
 * Receiver which runs in the Broker to listen for catalog updates from the
 * Coordinator. To prevent slowing initial queries, this class loads the
 * current catalog contents into the local cache on lifecycle start, which
 * avoids the on-demand reads that would otherwise occur. After the first load,
 * events from the Coordinator keep the local cache evergreen.
 */
@ManageLifecycle
public class CatalogUpdateReceiver
{
  private static final EmittingLogger LOG = new EmittingLogger(CatalogUpdateReceiver.class);

  private final CachedMetadataCatalog cachedCatalog;

  @Inject
  public CatalogUpdateReceiver(
      final CachedMetadataCatalog cachedCatalog
  )
  {
    this.cachedCatalog = cachedCatalog;
  }

  @LifecycleStart
  public void start()
  {
    cachedCatalog.resync();
    LOG.info("Catalog update receiver started");
  }
}
